The invention relates to a method and a tunnel type furnace for calcining carbonaceous bodies, in particular electrodes such as electrodes for the electrolytic production of aluminum or steel.
In the following description, reference will be made, by way of example, to the manufacture of electrodes for the production of aluminum, it being understood that the invention may also be, with appropriate modifications, applied to the manufacture of other electrodes or generic carbonaceous bodies.
With tunnel type furnaces, preformed bodies to be calcined, comprising a mixture of a carbonaceous matter, such as petroleum coke, anthracite, carbon black, graphite, and the like, with a binder containing pyrolyzable substances, such as tars and/or pitches, are made to pass therethrough on trucks, and are heated in an oxidizing medium or atmosphere such that the volatile substances released from the decomposition and/or distillation of binder fractions can be burned off and the binder itself cokefied.
Such prior tunnel type furnaces have the drawback that, while most of the volatiles are burned off therein, not all of the volatile substances which are released by the binder are burned off, and for this reason, some of these substances comprising essentially organic volatiles, in particular aromatic hydrocarbons, are still exhausted to the atmosphere, resulting in a serious disadvantage from the standpoints of environmental pollution and safety of the working area.